Class LeNet

LeNet was an early promising achiever on the ImageNet dataset.
References:
- http://yann.lecun.com/exdb/publis/pdf/lecun-98.pdf
- https://github.com/BVLC/caffe/blob/master/examples/mnist/lenet.prototxt

MNIST weights for this model are available and have been converted from https://github.com/f00-/mnist-lenet-keras.